Dear Members of this forum, I have a question regarding Microsoft Exchange Server 2003, I would appreciate if the experienced and professional IT members of this forum clarify my confusion. I have a Local Network indomain environmentin which there are client computers running WinXP OS and also has a Domain Controller which acts as a DHCP and DNS Server as well. I have just added a Mail Server in that local domain and than I installed a Microsoft Outlook on the client computers and configured the smtp address of the local Mail Server in the "Outgoing Mail Server" field of the Microsoft Outlook and added the POP3 address in the Incoming Mail Server field. Now I have connected the local network with internet . Now I try to send e-mails from my Microsoft Outlook to a friend who has an account on yahoo or hotmail. My question is that do I have to register my local domain on .com domain on internet inorder to be able to send e-mails from the Mail Server running in my local domain? How does this process take place? Will the .com domain provide a public IP address to my local domain and then register my domain nameto IP resolutionin there DNS database so that when I send e-mails from the Mail Server in my Local Domain, the ISP Service with which I am geting internet service can contact the .com domain and do a reverse look up for my local domain? Please correct me If I am wrong and if you have any additional information to provide kindly eleborate on it. Regards,

Hi, What your understanding is correct. If you just want to send the email to external users and no reverse DNS lookup feature is enabled on the opposite server, there is no necessary to register your domain on ISP. But if you also need to receive the email from the external users and the opposite server has enabled reverse DNS lookup function, the local domain must be registered on ISP so that they can find you in DNS. When we send the email, Exchange server first inquiry the MX record of the external email in DNS server, if the MX record is available, Exchange server will try to connect the opposite email server. Thanks Allen

Hi, By opposite Server do you mean the destination Mail Server? You mean to say that if the "Reverse Lookup Zone" feature is enabled on the destination Mail Server eg.Hotmail or Yahoo Mail Server than I donot have to register my local domain on ISP DNS database when sending e-mails? Butin case of receiving e-mails ,I have tomake sure that the local domain is registered on the ISPDNS database so that the e-mails could enter my mailbox in the local Mail Server by allowing the DNS Server of the ISP to resolve the local domain name to IP address and than after connecting to the IP address it will ask for the IP address of the local Mail Server and than connect to the local Mail Server and then deliver the e-mail into it. I hope my point is clear.

Hi, Yes, the opposite Server is the destination Mail Server, such as Yahoo, or Hotmail. The second section is misunderstanding. What I mean is if the "Reverse Lookup Zone" feature is enabled on the destination Mail Server, we must register the local domain on ISP DNS rather than not register it when sending the email. Of course, in case of receiving email, you also have to register the local domain. Thanks Allen

Allen, Thanks for your explanation but the problem that I am having understanding is when we send e-mails. The question is that how can we enable the Reverse Lookup Zone on the yahoo or hotmail Mail Server since we donot have access to these Servers? Reverse Lookup Zone resolves the IP address to the domain name, right? Now I wanted to know that when I send e-mails from a Mail Server in my local domain to a friend who has e-mail on yahoo domain. Does the Reverse Look up Zone enabled on the destination Mail Server(e.g Yahoo) resolves the IP address of the local domain to its actual domain name inorder to push the e-mail into the Mail Server of yahoo because the Mail Server of Yahoo also needs to know what is the domain of the Source(Local) Mail Server.Please correct me If my understanding is wrong? Thanks once again

Hi Student1,In order to receive incoming email you will need to have (1) a valid domain name (2) mx records for that domain name (3) a working environment to receive and store/forward the received emails. From what I have been able to ascertain from your posts you have number 3 and you need to work on 1 and 2. So you will need to have a domain name I will use the example domain.com, your domain.com DNS records should include an MX record (mail exchangers) - this is what sends incoming email to your perimeter email host. This MX record should point to a valid A record which in most cases is mail. So an incoming message would be sent to domain.com and be given the MX response of mail.domain.com which would then resolve via A record to x.x.x.x (your IP address).Now for lab uses a valid domain name takes a different feel, since you can control the domain names that you have, you can also determine what is valid. On the internet you cannot do that. For example domain.local is not a valid dns name on the internet since there is no .local top-level domain. In a lab environment that does not require external email functionality you can easily simplify this by using false domains to send back and forth through a manipulated DNS, however this would require that you set up two environments that can send back and forth.Also if you are looking for a permanent type email solution you should look at getting static IP addresses, which normally come with small business type internet packages or for an additional fee. Otherwise you will need a dynamic dns solution which isn't always best.-matt

Hi, That is out of control since enable Reverse Lookup Zone is their businness. Yes, Reverse Lookup Zone resolves the IP address to the domain name. For this questions, we need to first understand that the function of Reverse Lookup Zone for Exchange. When we send one email to external domain, such as Yahoo, if the Reverse Lookup Zone is enabled, it first finds the IP address in your sending email, and resolves the IP to the domain name based on the DNS. Then compare this domain name withanother domain name in your sending email, check whether the two names are same. If so, this indicates your email server is real not fake. After that, the Yahoo will accept the email or else will be rejected. In other words, the Reverse Lookup Zone is used to prevent the spam email from accessing the email server. Thus, I recommend registering your email server in order to ensure we can send the email normally if the feature of Reverse Lookup Zone is enabled. Thanks Allen

Allen, Thanks for such useful information, I am understanding what you mean. You mean to say that when we send e-mails from a local Mail Server in a domain to external domain eg. Yahoo or Hotmail. The DNS Server on Yahoo Domain will look for the IP address of our domain inorder to find out from which Mail Server the e-mail is coming. It will check its DNS Server and when not able to find any info about IP address and domain ,then it will contact the root of .com domain and if not available there than since the ISP that I am using must have its DNS Server online, than the .com domain will send the request to the ISP DNS Server and than if I have got the local domain and its IP address registered on the ISP DNS Server than ISP DNS Server will resolve the IP address to domain name(Reverse Look Up)and the destination Mail Server of yahoo or hotmailin this way will know from which domain this e-mail was coming. In case of receiving e-mail from yahoo or hotmail into the local Mail Server in our domain, then since the IP address to domain resolution for the Yahoo and Hotmail domain is already registered in its DNS database so it gets resolved by Reverse Look Up Zone without any problem but when the e-mail reaches our local Mail Server, the ISP DNS checks domainnameto IP address for the local domain and after connecting to that IP address itthan looks for the IP address of the local Mail Server inorder to connect to it and push the e-mail into the mailbox of the user . I hope my explanation makes sense. Please reply if you agree with my post. Thank you both once again,

Hi, Great, what your understanding is correct. If you have any further questions, please just feel free to let me know. Thanks Allen

Well, if any question strikes my mind I'll definitely bother you again . Allen the problem is that I was doing MCSE 2003 track from an Institute but there are several things regarding this track that I have forgotten . But anyways thanks again. Regards,

Hi, It's my pleausre to provide the useful information for you. Thanks Allen